Protective metal cap for plastic fuze radomes

ABSTRACT

In combination with a plastic fuze radome, a structure for protecting the internal electronic components housed within said fuze during flight said structure being a metal cap immersed in the forward tip of the radome and having a concave frontal indentation for reducing the droplet flow of impinging rain and other fluid around the cap, whereby the immersion of the metal cap in the plastic material of the radome prevents relative movement of the cap with respect to the components and thus avoids malfunctioning of the fuze via this disturbance and whereby the metal cap having a plastic coating avoids triboelectric charging of the radome, and, because of the thermal conductivity of the metal cap provides protection against surface heat buildup. Several openings are provided in the metal cap such that radial movement of the cap with respect to the components is prevented when said fuzes are subjected to spin forces. Extending from the base of the metal cap is a finger member having indentation in the side thereof for the purpose of securing the cap within the plastic of the radome.

llnited States Patent [191 Clark, J r.

[111 3,7fi0,66t

[ Dec. 25, 1973 PROTECTKVE METAL CAP FOR PLASTIC FUZE RADOMES [75] Inventor: Samuel A. Clark, .lr., Wheaton, Md.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: June 30, 1972 [21'] Appl. No.: 267,886

[52] US. Cl 102/702 P, 343/872 [51] lint. CL... F4212 13/041, F42C 13/00, F42c 19/00 [58] Field of Search 102/702 P [56] References Cited UNlTED STATES PATENTS 2,995,089 8/1961 Custer et a1. 102/702 P 3,008,415 11/1961 Foley 102/702 P Primary ExaminerBenjamin A. Borchelt Assistant Examiner-Thomas H. Webb Attorney-Harry M. Saragovitz et a1.

[57] ABSTRACT fuze via this disturbance and whereby the metal cap having a plastic coating avoids triboelectric charging of the radome, and, because of the thermal conductivity of the metal cap provides protection against surface heat buildup. Several openings are provided in the metal cap such that radial movement of the cap with respect to the components is prevented when said fuzes are subjected to spin forces. Extending from the base of the metal cap is a finger member having indentation in the side thereof for the purpose of securing the cap within the plastic of the radome.

10 Claims, 3 Drawing Figures PROTECTIVE METAL CAP FOR PLASTHC FUZE RADOMES RIGHTS OF THE GOVERNMENT The invention described herein may be manufactured, used, and licensed for or by the US. Government for governmental purposes without the payment to the inventor of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates generally to artillery fuze radomes which are used as a protective structure for the electronic components located in the nose of such a fuze. Specifically this invention relates to artillery fuze radomes ordinarily made from thermoplastic material. This invention is specifically related to the class of thermoplastic radomes wherein a metal cap is used in combination with a thermoplastic protective structure for a fuze.

First, thermoplastics are used for a manufacturing material for these artillery fuze radomes because of their desirable electrical and mechanical properties, low cost, and amendability to mass production. A major problem with thermoplastics is their limited ability to protect the fuze during flight from the combined effects of aerodynamic heating and erosion due to rain, dust, and other dense materials within the atmosphere. Erosion of the radome due to these solid materials causes degradation of the accuracy of the electronic fuze mechanisms for range findings or significant damage to the electronic components therein.

Different thermoplastic radomes exhibit varying deterioration rates when subjected to dust or rain impingment. This deterioration can be delayed somewhat by increasing the thickness of the radome tip. However, military specifications with regards to artillery fuze radomes do not allow sufficient material to be added to the tip in order to survive the complete flight profile from the foremost gun fire conditions.

A valid means of protecting thermoplastic radomes from erosion and degradation is to use a metal cap. l-leretofore these caps have been designed such that they were exterior to the radomes. Fuzes incorporating this particular design of cap when subjected to high voltage surface charging cause a significant percentage of electronic fuze malfunctions due to corona discharge of the electrical surface charge. Moreover, when such a cap design as the foregoing was subjected to spin and surface heating due to gun fire, in a significant number of cases, the cap disengaged from the radome.

The invention described herein overcomes many of the disadvantages of the foregoing constructions.

It is therefore the object of this invention to provide a new and novel protective structure for internal fuze components.

It is yet another object of this invention to provide a new and novel protective structure for internal fuze components in combination with a plastic fuze radome wherein said structure and said radome are prevented from relative movements with respect to said components. It is yet an additional object of this invention to provide a new and novel protective structure for internal fuze components which avoids triboelectric charging and corona discharging.

It is another object of this invention to provide a new and novel protective structure for internal fuze components which reduces droplet flow of impinging fluid around the radome.

It is still an additional object of this invention to provide a protective metal cap structure immersed and coated with a thermoplastic in combination with a plastic fuze radome such that said stress cracking of said radome is prevented.

It is yet an additional object of this invention to provide a protective structure for internal fuze components in combination with a plastic fuze radome wherein said structure comprises a metal cap such that said components are insulated from radome surface heat blocks.

These and other objects of the present invention will become more fully apparent with reference to the following specifications and drawings which relate to a preferred embodiment of the invention described herein.

SUMMARY A protective structure for internal fuze components in combination with a thermoplastic fuze radome comprises a metal cap having a concave surface formed into the top thereof and having a plastic coating, wherein said cap is congruently immersed into the thermoplastic radome. The metal cap has holes therein for preventing relative movements of the cap with respect to the component of the fuze. Rounded edges are provided on the metal cap for preventing stress cracking of the radome. The protective structure further comprises a projecting member attached to the underside of the metal cap, wherein the said member has a radial grove formed therein such that upon immersing in said plastic radome movement along the principle axis of the fuze is prevented and wherein said finger member provides a means for mounting the metal cap for encapsulation.

BRIEF DESCRIPTION OF THE DRAWING The specific nature of the invention as well as other objects, aspects, uses, and advantages thereof will clearly appear from the following descriptions and from the accompanying drawings, in which:

FIG. la is an illustration of a cut away view of the protective structure in combination with a thermoplastic fuze radome before the mounting finger is removed.

FIG. 1b is an illustration of a cut away view of the protective structure in combination with a thermoplastic fuze radome after the mounting finger is removed.

FIG. 10 is a detailed illustration of the protective structure for internal fuze components in combination with a thermoplastic fuze radome.

These and other objects of the present invention will become more fully apparent with reference to the following specifications and the drawings which relates to a preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will be easily understood in broad aspects by reference to FIG. 1a wherein there is illustrated a cut away view of the protective structure immersed in a thermoplastic fuze radome. In this figure the protective structure 20 is immersed coaxially in the plastic fuze radome 8. Mounting finger l6 protrudes from the inside surface of radome 8 into the cavity 40 for housing fuze components. Mounting finger 16 is used to hold the protective structure 20 during encapsulation. FIG. lb illustrates the protective structure 20 in combination with the thermoplastic fuze radome 8. The mounting finger 16 has been removed and only the radial lip 7 remains. The radial lip 7 is flush with the inside surface of the radome 8.

In FIG. 1c is shown a detail illustration of the protective structure in combination with a thermoplastic fuze radome. Immersed coaxially in plastic fuze radome 8 is metal cap 20. Metal cap 20 comprises a concave top surface I, a leading surface 2 forming an acute angle with respect to the underside of said cap and holes 4 formed therein. Projecting along the principle axis P-P' from the base 15 of the metal cap 20 is a protruding member 14 having concave indentation 5 and groove 6 therein. Concave indentation 5 is encapsulated by thermoplastic radome 8 and is included to further secure the cap into the tip of the radome. Groove 6 is formed on to the mounting member 16 for attachment to a molding machine. Groove 6 is designed to allow for removal of 16 and yet possess enough structural strength to survive molding pressure. Mounting member 16 is tapered along the surface 16 to prevent binding during molding.

The concave top 1 of metal cap 20 reduces impinging droplet flow around and down terminating edge 3 once the protective layer of the thermoplastic radome 8 has deteriorated. The leading edge 2 of the metal cap 20 restricts under cutting of droplet flowing down the side of the radome 8. Rounded corners such as corners 7 and 19 and 3 serve to prevent stress cracking of the surrounding thermoplastic material. Holes 4 formed into the base of the metal cap being encapsulated prevent rotation and thus secures the metal cap within the thermoplastic radome 8. Concave indentation 5 serves to secure the cap 20 from movement along the P-P' axis.

The inventor wishes it to be understood that he does not desire to be limited to the exact details of construction shown and described herein for obvious modifications will occur to a person skilled in this art.

What ls Claimed ls:

1. In combination with a thermoplastic fuze radome of the type wherein the radome is shaped in the form of a cone and used as a protective cover for the electronic components located in the nose ofa fuze, the improvement which comprises:

a. A solid cap embedded in said radome and having a flat underside and a topside; and

b. A projecting member attached to said underside and having a concave indentation extending around said member in a direction parallel to said underside whereby said indentation is filled with the thermoplastic of said radome to rigidly hold said member in place against axial movement.

2. The fuze radome of claim 1 further comprising a removable tapered finger attached to said member, said finger having a groove extending around said finger in a direction parallel to said underside and near the point of attachment to said member whereby said groove facilitates removal of said finger after said cap has been rigidly embedded in said radome.

3. The fuze radome of claim 2 wherein said cap has a centrally located depression in the topside thereof.

4. The fuze radome of claim 3 wherein the peripheral surface of said topside forms an acute angle with said underside.

5. The fuze radome of claim 4 wherein said underside has openings therein whereby said openings are filled with thermoplastic of said radome to rigidly hold said cap against rotational movement.

6. The fuze radome of claim 5 wherein said cap is comprised of metal.

7. The fuze radome of claim 5 wherein said depression is a circular concaved depression.

8. The fuze radome of claim 5 wherein at least one edge of said cap is rounded.

9. The fuze radome of claim 5 wherein said finger has at least one slot at the end thereof oriented in a plane transverse to the underside of said cap.

10. The fuze radome of claim 5 wherein said openings are blind holes. 

1. In combination with a thermoplastic fuze radome of the type wherein the radome is shaped in the form of a cone and used as a protective cover for the electronic components located in the nose of a fuze, the improvement which comprises: a. A solid cap embedded in said radome and having a flat underside and a topside; and b. A projecting member attached to said underside and having a concave indentation extending around said member in a direction parallel to said underside whereby said indentation is filled with the thermoplastic of said radome to rigidly hold said member in place against axial movement.
 2. The fuze radome of claim 1 further comprising a removable tapered finger attached to said member, said finger having a groove extending around said finger in a direction parallel to said underside and near the point of attachment to said member whereby said groove facilitates removal of said finger after said cap has been rigidly embedded in said radome.
 3. The fuze radome of claim 2 wherein said cap has a centrally located depression in the topside thereof.
 4. The fuze radome of claim 3 wherein the peripheral surface of said topside forms an acute angle with said underside.
 5. The fuze radome of claim 4 wherein said underside has openings therein whereby said openings are filled with thermoplastic of said radome to rigidly hold said cap against rotational movement.
 6. The fuze radome of claim 5 wherein said cap is comprised of metal.
 7. The fuze radome of claim 5 wherein said depression is a circular concaved depression.
 8. The fuze radome of claim 5 wherein at least one edge of said cap is rounded.
 9. The fuze radome of claim 5 wherein said finger has at least one slot at the end thereof oriented in a plane transverse to the underside of said cap.
 10. The fuze radome of claim 5 wherein said openings are blind holes. 